1. Field of the Invention
This invention relates to a method and apparatus for heating bulk materials in a drum.
Many materials that are shipped in pails or drums solidify during storage and/or shipping and must be melted or at least liquified, before they can be removed from their containers.
Examples are lards, butter and margarine, shortenings and hydrogenated vegetable oils, peanut butter, chocolate coatings and other fat-based confectionery materials. Waxes and heavy oils and gels are other examples of materials that require heating before they can be pumped from their shipping containers.
There are also a number of products that must be stored and shipped in a chilled or frozen form in order to preserve them. Examples are fruit purees, juices, fruit and vegetable concentrates and liquid eggs.
Some products will become semi-solids during storage because one or more of the components crystallizes. Examples are chocolate coatings, honey and syrups that contain blends of different sugars.
In all of the examples mentioned above, it is necessary to melt, soften or re-dissolve the materials before they can be pumped from their containers and used in further processing.
2. Description of the Prior Art
One common method, used in the food industry, is to place the containers in a heated room at a temperature as high as 140.degree. F. and allow them to melt or thaw over a period of several days. A number of "hot boxes" that heat four or eight drums at a time, are regularly advertised in the trade papers. These treatments will cause local overheating, due to the fact that the contents are not agitated and heat has to penetrate from the outside to the interior. There are dangers that spoilage or heat-induced deterioration will occur before the whole container is liquified.
Another method is to use a so-called drum heater. This is an electrically heated collar that is clamped around the container, commonly a steel drum. This method can cause severe local overheating that can have deleterious effects on the quality of the material. The process is slow and the collar should be moved a number of times to melt different sections in the drum. There is no agitation during the melting process.